Imaging system for fuel tank analysis

ABSTRACT

A method can include generating image data of an interior of a fuel tank disposed within a wing of an aircraft, and determining, by a processing device, an amount of wing bending of the wing of the aircraft based on the generated image data of the interior of the fuel tank. The method can further include producing, by the processing device, a fuel measurement value representing an amount of fuel contained in the fuel tank based on the amount of wing bending of the wing of the aircraft, and outputting, by the processing device, an indication of the fuel measurement value.

BACKGROUND

The present invention relates to fluid storage systems, and inparticular to determining properties of fuel tanks and their contents.

In fuel systems such as those on aircraft, for example, it is desirableto accurately determine properties related to fuel tanks, such as thevolume and/or mass of fuel remaining. These tanks may exist in complexenvironments, such as the wing of the aircraft, for example. Variousfactors may affect the orientation of fuel within these tanks, such astilt of the aircraft and bending of the wing. It is desirable to knowhow each of these factors are presently affecting a tank, so as tofacilitate accurate determination of remaining fuel.

Prior art systems have implemented capacitive probes within fuel tanks,for example, to determine the volume of remaining fuel. Electromagneticfields are utilized by the probes to determine the level of fuel withinthe tank, which may then be used to calculate a remaining fuel volume.However, due to strict regulations, the amount of energy permittedwithin a fuel tank is limited, constraining the number of probes thatmay be utilized. Moreover, a number of capacitive and/or other probes(e.g., densitometers, temperature probes, or other probes) required tobe installed for accurate determination of a remaining fuel volume canresult in significant installation and maintenance costs. Therefore, itdesirable to implement an improved system for determining properties offuel tanks.

SUMMARY

In one example, a method includes generating image data of an interiorof a fuel tank disposed within a wing of an aircraft, and determining,by a processing device, an amount of wing bending of the wing of theaircraft based on the generated image data of the interior of the fueltank. The method can further include producing, by the processingdevice, a fuel measurement value representing an amount of fuelcontained in the fuel tank based on the amount of wing bending of thewing of the aircraft, and outputting, by the processing device, anindication of the fuel measurement value.

In another example, a device includes at least one processor andcomputer-readable memory. The computer-readable memory can be encodedwith instructions that, when executed by the at least one processor,cause the device to: receive image data of an interior of a fuel tankdisposed within a wing of an aircraft; determine an amount of wingbending of the wing of the aircraft based on the received image data ofthe interior of the fuel tank; produce a fuel measurement valuerepresenting an amount of fuel contained in the fuel tank based on theamount of wing bending of the wing of the aircraft; and output the fuelmeasurement value.

In another example, a system includes one or more image capturingdevices, at least one processor, and computer-readable memory. The oneor more image capturing devices can be located to generate image data ofan interior of a fuel tank disposed within a wing of an aircraft. Thecomputer-readable memory can be encoded with instructions that, whenexecuted by the at least one processor, cause the system to: generate,using the one or more image capturing devices, the image data of theinterior of the fuel tank disposed within the wing of the aircraft;determine and amount of wing bending of the wing of the aircraft basedon the generated image data of the interior of the fuel tank; produce afuel measurement value representing an amount of fuel contained in thefuel tank based on the amount of wing bending of the wing of theaircraft; and output the fuel measurement value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a fuel tank monitoring system thatincludes imagers for determining properties of the fuel tank

FIGS. 2A and 2B are diagrams illustrating a reference image and anactive image, respectively, for a fuel tank monitoring system.

FIG. 3 is a diagram illustrating a fuel tank that includes imagershaving opposing fields of view.

FIGS. 4A and 4B are diagrams illustrating a wing of an aircraft with nobending, and with some bending, respectively.

FIGS. 5A and 5B are diagrams illustrating a reference image and anactive image, respectively, for determining the bend of an aircraftwing.

FIG. 6 is a diagram illustrating a fuel tank that includes a lidarimager for determining properties of the fuel tank.

FIG. 7 is a diagram illustrating a fuel tank that includes an imager fordetermining a density of fuel within the fuel tank.

FIGS. 8A and 8B are diagrams illustrating a fuel tank that includesimagers for detecting properties of the ullage gasses within the fueltank.

FIGS. 9-13 are flow diagrams illustrating example operations fordetermining properties of a fuel tank utilizing one or more imagecapture devices.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating fuel tank monitoring system 10, whichincludes fuel tank 12 disposed within aircraft wing 14. Fuel tankmonitoring system 10 includes imagers 16 a-16 j for determining fluidand/or physical properties of fuel tank 12. Wing 14 is oriented aboutcenterline C_(L) and includes trailing edge space 18, leading edge space20, and fuel tank 12. As illustrated in FIG. 1, fuel tank 12 is definedby spars 22, and upper and lower skins of wing 14. Wing 14 includesstructural members such as spars 22 and ribs 24, which may be internalor external to fuel tank 12, or may define boundaries of fuel tank 12.Ribs 24 may include structural elements 26, which are illustrated asholes within ribs 24. Fuel tank 12 may include many more structuralelements (i.e., physical features) not shown in FIG. 1, which may be inaddition to, or part of, spars 22 and ribs 24. While illustrated withinwing 14, fuel tank 12 may be any structure designed to hold a fluid.

Fuel tank monitoring system 10 may also include controller 28, which maybe operatively connected to provide two-way communication with imagers16 a-16 n. Controller 28 may be a microprocessor implemented within afuel avionics system, for example. In other embodiments, each imager 16a-16 j may include its own respective controller in addition to, or inreplacement of, controller 28. Controller 28, in some examples, caninclude one or more processors and computer-readable memory encoded withinstructions that, when executed by the one or more processors, causecontroller 28 and/or other elements of fuel tank monitoring system 10 tooperate in accordance with techniques described herein. Examples of suchprocessors can include any one or more of a microprocessor, acontroller, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), orother equivalent discrete or integrated logic circuitry.

Computer-readable memory of controller 28 can be configured to storeinformation within controller 28 during operation. Computer-readablememory, in some examples, can be described as a computer-readablestorage medium. In some examples, a computer-readable storage medium caninclude a non-transitory medium. The term “non-transitory” can indicatethat the storage medium is not embodied in a carrier wave or apropagated signal. In certain examples, a non-transitory storage mediumcan store data that can, over time, change (e.g., in RAM or cache). Insome examples, computer-readable memory of controller 28 can includetemporary memory, meaning that a primary purpose of thecomputer-readable memory is not long-term storage. Computer-readablememory of controller 28, in some examples, can be described as avolatile memory, meaning that the computer-readable memory does notmaintain stored contents when electrical power to controller 28 isremoved. Examples of volatile memories can include random accessmemories (RAM), dynamic random access memories (DRAM), static randomaccess memories (SRAM), and other forms of volatile memories. In someexamples, computer-readable memory can be used to store programinstructions for execution by one or more processors of controller 28.For instance, computer-readable memory of controller 28 can be used bysoftware or applications executed by controller 28 to temporarily storeinformation during program execution.

Imagers 16 a-16 j may be any image capture devices capable of producingan analog or digital image from received light at one or morewavelengths. Imagers 16 a-16 j may be, for example, cameras, short-waveinfrared imagers, thermal imagers, fiber optic bundles, or any otherdevice capable of capturing light to form an image. While illustrated aslocated on external surfaces of fuel tank 12, imagers 16 a-16 j may beimplemented anywhere internal or external to fuel tank 12. Imagers 16a-16 j may be located in positions so as to obtain a completetwo-dimensional and/or three-dimensional representation of fuel tank 12,or may be implemented to only obtain images of desired locations of fueltank 12. For example, fewer imagers 16 a-16 j may be implemented in fueltank 12, and the portions of tank 12 that are not captured in any fieldof view of imagers 16 a-16 j may be inferred based upon the knownstructure of fuel tank 12.

Imagers 16 a-16 j may provide image data to controller 28 to determineproperties of fuel tank 12. Image data may be obtained using any devicecapable of producing electronic data based upon incoming light such as,for example, a focal-plane array. The properties of fuel tank 12 mayinclude, but are not limited to, physical features of an interior offuel tank 12 (e.g., locations and/or physical contours of spars 22, ribs24, structural elements 26, or other physical features of the interiorof fuel tank 12), a level and/or volume of fuel within the interior offuel tank 12, tilt of an aircraft that includes fuel tank 12, an amountof bend of wing 14 of the aircraft, a density of the fuel within fueltank 12, a chemical composition of fluids within fuel tank 12 (e.g.,fuel, gases within an ullage of fuel tank 12, or other fluids withinfuel tank 12), and/or a temperature of fluid(s) within fuel tank 12. Toobtain these properties, processing may be performed on the image dataobtained by imagers 16 a-16 j. The focal-plane array or other imagesensing device of imagers 16 a-16 j may be configured to output an arrayof pixels, for example. The array of pixels may be provided to a localcontroller of imager 16 a-16 j, or controller 28, for processing.Controller 28 can utilize the determined properties of fuel tank 12 toproduce a fuel measurement value representing an amount of fuelcontained in fuel tank 12. The fuel measurement value can include, forexample, a volume of fuel, a mass of fuel (e.g., based on a volume anddensity of the fuel), or other fuel measurement values representing anamount of fuel contained in fuel tank 12. Controller 28 can output anindication of the fuel measurement value, such as by outputting dataspecifying the fuel measurement value via a communications data bus orother network (not illustrated), a visual indicator (e.g., a graphicalgauge, a warning light, or other visual indicator) of the fuelmeasurement value, or other indication of the fuel measurement value.

By utilizing imagers 16 a-16 j to determine properties of fuel tank 12,prior art capacitive probes may be eliminated (or a number of capacitiveprobes reduced) from fuel tank 12, which removes or reduces theelectromagnetic fields generated by the capacitive probes. In exampleswhere imagers 16 a-16 j are implemented external to fuel tank 12,obtaining a field of view through, for example, a window, all electroniccomponents used for fuel volume determinations may be removed from fueltank 12. Further, many or all of the electronics for imagers 16 a-16 jmay be contained within leading edge space 20 and trailing edge space18, regardless of the imagers' locations inside or outside of fuel tank12. This can reduce the need for opening fuel tank 12 to provide servicefor imagers 16 a-16 j. Imagers 16 a-16 j may also be utilized to performinspections of the internals of fuel tank 12, further reducing the needfor entry into fuel tank 12. For example, image data obtained by imagers16 a-16 j may be utilized to perform routine inspections for corrosion,cracks or other maintenance needs within fuel tank 12.

FIGS. 2A and 2B are example images 30 a and 30 b captured by imager 16a. While illustrated as images 30 a and 30 b captured by imager 16 a,images 30 a and 30 b may be captured by any imager 16 a-16 j implementedfor fuel tank 12. Moreover, it should be understood that in someexamples, techniques described herein can utilize more than the twoimages 30 a and 30 b described with respect to the example of FIGS. 2Aand 2B. FIG. 2A illustrates reference image 30 a which may be areference for the field of view of imager 16 a. Reference image 30 a maybe taken at any reference time for fuel tank 12. For example, and asillustrated in FIG. 2A, reference image 30 a may be obtained by imager16 a during a time in which fuel tank 12 does not contain any fuel. Inother examples, reference image 30 a can be obtained by imager 16 aduring a time when fuel tank 12 contains fuel. Reference image 30 a mayalso be obtained while the aircraft is on the ground when fuel tank 12is at or near empty to help ensure that there is minimal wing bending,which may affect the orientation of physical features within fuel tank12. While illustrated as a reference image obtained while on the groundwith minimal fuel in fuel tank 12, reference image 30 a may be obtainedat any other time, such as when the aircraft is in air and/or when fueltank 12 contains fuel.

FIG. 2B illustrates active image 30 b which may be actively obtainedduring operation of fuel tank monitoring system 10 and/or the aircraftfor which fuel tank monitoring system 10 is implemented. Active image 30b depicts an instance in which fuel is present within fuel tank 12. Fuellevel lines 32 a-32 c are illustrated to depict a level of fuel on eachsurface of fuel tank 12 that is in the field of view of imager 16 a.Fuel level lines 32 a-32 c represent an interface between fuel andullage (i.e., an unfilled space of fuel tank 12 that can be occupied byone or more gases). Active image 30 b may be obtained using the sameimager 16 a-16 j that was used to obtain reference image 30 a.Therefore, images 30 a and 30 b may be processed by controller 28 todetermine at least the level of fuel in fuel tank 12.

Image processing may be performed by controller 28, for example, todetermine the location of fuel level lines 32 a-32 c. This imageprocessing may include feature recognition, edge detection, or any othertype of image recognition. Feature recognition, for example, may performan image-to-image overlay to compare active image 30 b to referenceimage 30 a in order to determine locations of the interior of fuel tank12 where images 30 a and 30 b do not match. Controller 28 may detectdisconnects from the overlay to determine where fuel level lines 32 a-32c are located.

Edge detection may also be utilized to detect fuel level lines 32 a-32c. Edge detection may be performed by searching active image 30 b forsharp changes in light intensity. For example, if image 30 b includes anarray of pixels, controller 28 may search the pixel array to detectadjacent pixels that have a significant difference in intensity. Oncecontroller 28 detects edges within fuel tank 12, a comparison may bemade to the known structure in the field of view of imager 16 a todetermine if the edges are indicative of the fuel interface. Forinstance, controller 28 can store a model of a shape of fuel tank 12,such as a model defined using computer aided design (CAD) technologiesthat includes relative locations of physical features of the shape offuel tank 12, including physical features corresponding to externalboundaries of, and internal physical features of, the interior of fueltank 12 (e.g., spars 22, ribs 24, structural elements 26, or otherphysical features of the interior of fuel tank 12). In addition tofeature and edge detection, any other image processing techniques, suchas the use of machine learning techniques (e.g., artificial neuralnetworks, Bayesian networks, support vector machines, or other types ofmachine learning techniques), may be utilized to process active images30 b to determine a location and/or intersection of fuel level lines 32a-32 c with physical features of the interior of fuel tank 12.

As illustrated in FIG. 2B, three fuel level lines 32 a-32 c may bedetermined from the field of view of imager 16 a. Active images fromother imagers 16 b-16 j may also be utilized to determine fuel levellines for each wall of fuel tank 12, for example. If locations of fuellevel lines are determined for each wall of fuel tank 12, the volume offuel may be determined. For instance, controller 28 can compare one ormore locations of the interior of fuel tank 12 corresponding to thedetermined fuel level lines that correspond to (e.g., intersect)locations of one or more physical features of the interior of fuel tank12 (e.g., determined based on reference image 30 a, a model of the shapeof fuel tank 12, or combinations thereof). Controller 28 can determine,in some examples, an amount of fuel that is between the determined fuellevel lines and a bottom of fuel tank 12 (i.e., a bottom of fuel tank 12as defined with respect to level flight of the aircraft). The tilt ofthe aircraft, for example, may also be determined by knowing the fuellevel lines for each wall of fuel tank 12. For example, if fuel levelline 32 a of image 30 b is higher than fuel level line 32 c, controller28 may be able to determine a tilt of the aircraft based on fuel levellines 32 a-32 c and the known geometry of fuel tank 12 (e.g., known viathe model of the shape of fuel tank 12).

FIG. 3 is a diagram that illustrates fuel tank 12 including imagers 40 aand 40 b. Imagers 40 a and 40 b are capable of viewing top portion 42 aand bottom portion 42 b of fuel tank 12, respectively, to detect a fuelinterface 44. Imagers 40 a and 40 b may include light sources 46 a and46 b, respectively. While illustrated in FIG. 3 as located inside fueltank 12, imagers 40 a and 40 b may also be located outside of fuel tank12 while still having a view of the inside structure of fuel tank 12through a window, for example. The field of view for each imager 40 aand 40 b is illustrated by the arrows in FIG. 3.

Imager 40 a may be located proximate to (e.g., attached to or otherwisedisposed proximate to) the top skin of wing 14, which may also be thetop boundary of fuel tank 12 in some examples. Imager 40 a may thereforehave a field of view that is capable of imaging bottom portion 42 b offuel tank 12. Imager 40 b may be located proximate to (e.g., attached toor otherwise disposed proximate to) the bottom skin of wing 14, whichmay also be the bottom boundary of fuel tank 12 in some examples. Imager42 a may therefore have a field of view that is capable of imaging topportion 42 a of fuel tank 12. Light sources 46 a and 46 b may beimplemented to illuminate the internal structure of fuel tank 12. Lightsources 46 a and 46 b may be any devices capable of emitting light atany desired wavelength or range of wavelengths such as, for example, alaser, a light-emitting diode (LED), or any other light emitter.

Imager 40 a may be submerged below fuel interface 44, for example. Inexamples where imager 40 a is submerged and the field of view of imager40 a originates beneath the top surface of the fuel, controller 28 maynot be able to detect fuel interface 44 within fuel tank 12 based on animage from imager 40 a. However, in such examples, imager 40 b that islocated with a field of view of upper portion 42 a can enable controller28 to detect fuel interface 44 based upon an image from imager 40 b.Detection of fuel interface 44 may be accomplished using any type ofimage processing techniques capable of detecting fuel interface 44 fromelectronic data obtained by imagers 40 a and 40 b, such as thetechniques discussed above. For example, an image-to-image overlay maybe used to determine a location and/or intersection of fuel level lineswith physical features of the interior of tank 12 to determine alocation of fuel interface 44. In other embodiments, imager 40 a may beimplemented outside fuel tank 12 such that imager 40 a is neversubmerged below fuel interface 44 and therefore, imager 40 b is notrequired to determine the location of fuel interface 44.

During other operational states, fuel interface 44 may be below thefield of view of imager 40 b. In such operational states, imager 40 a,located with a field of view that includes lower portion 42 b, canenable controller 28 to detect fuel interface 44 even though it is belowthe level of imager 40 b. Hence, all possible locations of fuel boundary44 may be detected within fuel tank 12 utilizing imagers 40 a and 40 b.

Light sources 46 a and 46 b may be controlled in any desirable manner toilluminate fuel tank 12 for imagers 40 a and 40 b. Although illustratedas integral to imagers 40 a and 40 b, light sources 46 a and 46 b mayalso be implemented as devices separate from imagers 40 a and 40 b.Because imagers 40 a and 40 b produce image data based upon collectedlight, it may be desirable to control an intensity, and direction, oflight within fuel tank 12. For example, light source 46 a can be turnedon to provide reflective light for detecting fuel interface 44 by imager40 a and/or transmissive light for detecting fuel interface 44 by imager40 b. Light source 46 b can be turned on to provide transmissive lightfor detecting fuel interface 44 by imager 40 a and reflective light fordetecting fuel interface 44 by imager 40 b. In other embodiments, bothlight sources 46 a and 46 b may be turned on for detection of fuelinterface 44 by one or more of imagers 40 a and 40 b. Similar operationof light sources 46 a and 46 b may be performed for any other imagerimplemented within fuel tank 12.

FIG. 4A illustrates wing 14 with no bending, and FIG. 4B illustrateswing 14 with bending. Wing 14 includes imager 50 disposed therein, andalso includes structural elements 52 a-52 d (i.e. physical features ofthe interior of fuel tank 12). Imager 50 may be any type of imagecapture device, including any of those discussed in previousembodiments. Imager 50 may have a field of view illustrated by thearrows extending from imager 50 in FIGS. 4A and 4B. This field of viewmay be such that imager 50 is able to obtain image data that includesall of structural elements 52 a-52 d relative to one another. With nobend, wing 14 remains oriented about centerline C_(L). With bending, thetip of wing 14 is displaced below centerline C_(L) and is oriented abouta bend line C_(B). The angle θ_(B) is the angle between centerline C_(L)and bend line C_(B). While illustrated as bending downward, which mayoccur during refueling of an aircraft on the ground, for example, wing14 may also bend upward during flight.

Wing bending may be important in determining a level of fuel within fueltank 12 because the orientation of fuel within fuel tank 12 may bealtered due to bending in wing 14. In addition to determination of fuellevels, a determination of wing bending of wing 14 may be useful forother systems of an aircraft. Because imager 50 may be utilized todetect wing bending in addition to detecting fuel levels as described inthe previous embodiments, no extra systems need to be implemented on theaircraft to detect wing bending.

FIG. 5A illustrates an example reference image 53 a obtained by imager50 while wing 14 has no bend (e.g., for the embodiment illustrated inFIG. 4A), and FIG. 5B illustrates an active image 53 b obtained byimager 50 while wing 14 has a bend of θ_(B) (e.g., for the embodimentillustrated in FIG. 4B). While illustrated as holes within structuralelements 52 a-52 d, any other structural members may be compared to oneanother to determine an amount of wing bending θ_(B). While illustratedas ribs of wing 14, structural elements 52 a-52 d may be any structuralelements within wing 14 that may be viewed relative to one another. Inaddition, while illustrated as located to have a field of view thatextends generally in a direction from a root to a tip of wing 14, imager50 (or any one or more additional imagers) can be located to have afield of view of any portion of the interior of fuel tank 12, such thatcontroller 28 can determine an amount of wing bending of wing 14 basedon relative displacement of physical features of the interior of fueltank 12 based on the generated image data from the one or more imagers,as is further described below.

Images 53 a and 53 b include distances 54 a-54 c. Distance 54 a is thedistance between the bottom edge of the hole in structural element 52 aand the bottom edge of the hole in structural element 52 b. Distance 54b is the distance between the bottom edge of the hole in structuralelement 52 b and the bottom edge of the hole in structural element 52 c.Distance 54 c is the distance between the bottom edge of the hole instructural element 52 c and the bottom edge of the hole in structuralelement 52 d. While illustrated as three distances 54 a-54 c, any numberof comparisons between structural elements of wing 14 may be utilized toachieve a desired accuracy of the detected wing bending.

The angle θ_(B), illustrated in FIG. 4B, may be determined by comparingdistances 54 a-54 c of image 53 b, with distances 54 a-54 c of image 53a to determine a relative displacement between structural elements 52a-52 d that can correspond to an amount of wing bending of wing 14.Controller 28, or any other controller, may accomplish this by using anyform of image processing, such as those discussed above. Image 53 b maybe compared to image 53 a using an image-to-image overlay, for example,and the difference between distances 54 a-54 c of images 53 b and 53 amay be determined. In another embodiment, if the base distances 54 a-54c are known (e.g., via a model of a shape of fuel tank 12 that specifiesrelative locations of physical features of the interior of fuel tank12), other forms of image processing may be utilized to determinedistances 54 a-54 c of image 53 b, and those distances 54 a-54 c may becompared to the base values to determine an amount of wing bendingθ_(B). While the embodiment discussed with reference to FIGS. 4A-5B maybe utilized to detect a single angle θ_(B), the techniques describedherein may be applied to detect higher-dimensional properties of wingbending by using, for example, three-dimensional modeling of wing 14based on images obtained from imagers positioned within wing 14.

Controller 28 can utilize the determined amount of wing bending θ_(B) todetermine a fuel measurement value representing an amount of fuelcontained in fuel tank 12, such as a fuel volume, a fuel mass, or otherfuel measurement values representing an amount of fuel contained in fueltank 12. For instance, controller 28 can store and/or determine a modelof a shape of fuel tank 12, such as a model defined by CAD or othertechniques that specified relative locations of physical features of theinterior of fuel tank 12. Controller 28 can determine the fuelmeasurement value based on the determined amount of wing bending θ_(B),such as by modifying the shape of fuel tank 12 using the model of theshape of fuel tank 12 and determining the fuel measurement value basedon the modified shape. For instance, controller 28 can modify thelocations of physical features of the interior of fuel tank 12 withinthe model based on the determined amount of wing bending θ_(B).Controller 28 can determine the fuel measurement value representing theamount of fuel contained in fuel tank 12 based on the a location of fueland ullage (e.g., associated with one or more of fuel level lines 32a-32 c, or more fuel level lines) corresponding to (e.g., intersecting)locations of one or more of the physical features of the interior offuel tank 12 defined using the modified shape within the model.

FIG. 6 is a diagram illustrating fuel tank 12 that includestime-of-flight imager 60. Time-of-flight imager 60 may be implemented asa Light Detection and Ranging (lidar) device or any other image capturedevice capable of measuring a time-of-flight of reflected light.Time-of-flight imager 60 may emit light 64 outward from time-of-flightimager 60 using a built-in, or separate, directional light source asillustrated by the arrows in FIG. 6. Light 64 may be emitted utilizing alaser, or any other light source capable of emitting light at a knownwavelength. Lasers provide a directed light source that can be emittedtoward fuel interface 62. Light 64 is reflected off of fuel interface 62and may be obtained and analyzed by controller 28, for example. Asillustrated in FIG. 6, other features, such as spars 22 and structuralfeatures 26 may also be detected by time-of-flight imager 60 based uponreflected light.

Time-of-flight imager 60 may include a focal plane array, for example,that provides an image on a pixel-by-pixel basis. For each pixel, atime-of-flight may be determined based upon a known time of sending outlight 64 by the laser or other light source of time-of-flight imager 60.Any type of time-of-flight detection may be utilized such as, forexample, range gating or direct time-of-flight to provide an indicationof time-of-flight for each pixel. For example, for range gating, thetime-of-flight may be indicated based upon an intensity of the pixel,whereas for direct time-of-flight, the actual time-of-flight for thelight to travel from the light source and back to the imager is measuredfor each pixel.

In another embodiment, the phase of the reflected light 64 may be usedby time-of-flight imager 60 to determine, on a pixel-by-pixel basis, thetime-of-flight for light 64 to travel from the light source back toimager 60. For example, when light is reflected off of an interface,such as fuel interface 62, the phase of the light is shifted based uponthe distance the light traveled prior to reflection. Therefore, thephase of light for each pixel may be utilized to determine atime-of-flight for each pixel.

By knowing the time-of-flight for each pixel obtained by the imager oftime-of-flight imager 60, a three-dimensional image of fuel tank 12 maybe determined (e.g., by controller 28). Controller 28, utilizing thegenerated three-dimensional image data, can determine three-dimensionalproperties of fuel tank 12, such as a location of physical features ofthe interior of fuel tank 12, a location of fuel interface 62 (i.e.,representing an interface between fuel and ullage of fuel tank 12), alocation of fuel interface 62 corresponding to (e.g., intersecting) thephysical features of the interior of fuel tank 12, a tilt of theaircraft including fuel tank 12, a bending of wing 14 including fueltank 12 (e.g., based on a relative displacement of the identifiedphysical features of the interior of the fuel tank 12 as compared to amodel of the shape of fuel tank 12), or other three-dimensionalproperties of fuel tank 12. Such three-dimensional data can enablecontroller 28 to determine a fuel measurement value corresponding to anamount of fuel contained in fuel tank 12 without comparison to orgeneration of reference images of the interior of fuel tank 12. Forexample, fuel interface 62 is illustrated in FIG. 6 with tilt,indicating that the aircraft carrying fuel tank 12 is tilted withrespect to the local acceleration vector of the aircraft. By generatinga three-dimensional image of fuel tank 12, the tilt of fuel interface 62may be determined with great precision. While illustrated internal tofuel tank 12, time-of-flight imager 60 may be implemented anywhere inwhich it is possible to get an internal image of fuel tank 12, such asexternal to fuel tank 12 through a window, for example. Time-of-flightimager 60 may also be utilized in any of the previous embodimentsdisclosed to detect fuel levels, wing bending, tilt, or any otherproperties of fuel tank 12.

In addition to time-of-flight imaging, any of the imagers illustrated inFIGS. 1-6 may be configured to determine a fuel interface or otherproperty of a fuel tank based on a pattern of light. For example,instead of a lidar device that measures time of flight from one or morelight pulses, imager 60 of FIG. 6 may be configured to project a patternof light in fuel tank 12. This pattern may be, for example, severalbeams of light projected in different, but known, directions. All beamsmay be configured to hit fuel interface 62 regardless of the level offuel in fuel tank 12. Because the beams are projected in differentdirections from the light source of imager 60, the pattern will changebased on the location and orientation of fuel interface 62 relative toimager 60. For example, if three light beams are emitted from the lightsource of imager 60, then three points on fuel interface 62 will reflectback to imager 60. Imager 60 may produce an image that illustrates thethree reflected points. Using the three reflected points, as well as theknown direction of the beams from imager 60, a location and orientationof fuel interface 62 may be determined.

FIG. 7 is a diagram illustrating fuel tank 12 that includes light source70 and imager 72 utilized to determine a density of fluid (e.g., fuel)within fuel tank 12. Imager 72 may be any image capture device such asthose discussed in the above embodiments. Light source 70 may be anylight source, such as any of those discussed in the above embodiments.While illustrated as external to fuel tank 12 in wing space 20, imager72 may be located at different positions external to or internal to fueltank 12

Refraction of the light emitted from light source 70 after the lightpasses through an interface with fuel contained in fuel tank 12 may beutilized to determine a density of the fuel within fuel tank 12. Forinstance, as in the example of FIG. 7, the interface with the fuelcontained in fuel tank 12 can be an interface between the fuel and gaswithin an ullage of fuel tank 12. In other examples, such as when lightsource 70 is located at a position that may typically be submerged belowa level of fuel contained in fuel tank 12, the interface with the fuelcontained in fuel tank 12 can include an interface between, e.g., awindow separating light source 70 and fuel contained in fuel tank 12.

As illustrated in FIG. 7, a directed beam of light 78 emitted by lightsource 70 may be aimed at one of spars 22, or any other structuralelement of fuel tank 12, for example. Location 76 a may be the locationof the interior of fuel tank 12 that beam 78 hits (i.e., intersects)after traveling through fuel interface 74. Location 76 b may be alocation of the interior of fuel tank 12 corresponding to non-refractionof beam 78, such as the location that beam 78 hits (i.e., intersects)after traveling through fuel tank 12 when fuel tank 12 is empty of fuel(illustrated by the dashed line in FIG. 7). Angle θ₁ is the angle ofbeam 78 above fuel interface 74 relative to normal L_(N). Angle θ₂,which can be considered a refraction angle of beam 78 after beam 78passes through the interface with the fuel (fuel interface 74 in thisexample), is the angle of beam 78 relative to normal L_(N) below fuelinterface 74. Angle θ₁ may be known based on the installed location anddirectional orientation of light source 70. If the level of fuelinterface 74 is also known, the distance D₁ may be utilized to determineangle θ₂. This may be advantageous when measuring the density of fuel,for example, prior to takeoff when the level of fuel interface 74 isknown.

Imager 72 may be implemented to receive reflected light 80 to determineposition 76 a. Position 76 a may be determined by controller 28, forexample, using image processing techniques, such as those discussed inthe above embodiments. Location 76 b may be a known reference locationindicative of non-refraction of beam 78, such as the location of theinterior of fuel tank 12 that beam 78 hits when there is no fuel in tank12. By comparing the determined location 76 a obtained from the imagedata to the reference location 76 b, distance D₁ may be calculated. Forexample, controller 28 may process an image-to-image overlay of a firstimage that includes the detected location 76 a, and a reference imagethat includes reference location 76 b to determine a distance betweenlocations 76 a and 76 b within the overlay. Using a model of theinternals of tank 12, for example, the determined distance within theoverlay may then be correlated to the actual physical distance D₁. Usingdistance D₁, and the known level of fuel interface 74, θ₂ may bedetermined by controller 28. Using both θ₁ and θ₂, controller 28 canutilize Snell's law to determine the refractive index of the fuel. Afterobtaining the refractive index, known properties of the fuel within fueltank 12, along with a sensed temperature of the fuel, may be utilized tocalculate the density of the fuel based on the refractive index.

To calculate the density from the refractive index, the temperature ofthe fuel must be known, as temperature is also a variable that affectsrefractive index. To obtain temperature, a temperature probe (not shown)may be implemented to sense the temperature of the fuel. In anotherembodiment, imager 72 may be implemented, for example, as a far infraredimager, or any other thermal imager, to detect blackbody radiation. Afar infrared imager, for example, may produce electronic data indicativeof temperature in its field of view. Each pixel, for example, may havean intensity that is directly proportional to the temperature of theobjects within the image. A thermal imager is also capable of receivingthe radiation of beam 80 to determine location 76 a. This way, both theangle of refraction and the temperature, and thus the density of fuel,may be obtained using a single imager 72. Although described in thepresent embodiment for imager 72, a thermal imager may be implemented inany of the above embodiments to both obtain images of fuel tank 12 aswell as determine the temperature of the contents of fuel tank 12.

Controller 28 can determine a fuel measurement value representing anamount of fuel contained in fuel tank 12 based on the determined densityof the fuel. For instance, controller 28 can determine a fuelmeasurement value representing a mass of fuel contained in fuel tank 12based on the determined density and a determined volume of the fuelcontained in fuel tank 12. Accordingly, techniques described herein canenable a density of fuel contained within fuel tank 12 using imagingtechniques, thereby enabling fuel measurement values, such as a mass offuel contained in fuel tank 12, to be determined.

FIGS. 8A and 8B are diagrams illustrating imagers 92 and 100,respectively, implemented to determine properties of ullage gases 96.FIG. 8A illustrates fuel tank 12 that includes light source 90 andimager 92. Fuel interface 94 separates the fuel in tank 12 from ullagegases 96. Light source 90, which may be any light source such as thosedescribed in the above embodiments, may be configured to producedirectional light beam 98 for receipt by imager 92. FIG. 8B illustratesan imager 100 that includes a local light source, which produces lightbeam 102 that is directed at the opposing spar 24 and reflected back forreceipt by imager 100. In each of the embodiments illustrated in FIGS.8A and 8B, imagers 92 and 100 may be utilized to determine theabsorption of at least one wavelength of beams 98 and 102, respectively.

Absorption of light is dependent upon the medium through which the lighttravels. Therefore, if beams 98 and 102 remain solely within ullagegases 96, properties of ullage gases 96 may be determined by controller28, for example, based on the amount of absorption of at least onewavelength of beams 98 and 102. Aircraft systems may include inert gasgenerating systems configured to produce oxygen-depleted air for thefuel tank ullage to reduce the probability of combustion within the fueltank. In particular, it is desirable to ensure that oxygen levels remainbelow a threshold percentage of ullage gases 96. In the example of FIGS.8A and 8B, fuel tank monitoring system 10 can include and/or beoperatively coupled to such an inert gas generating system the producesoxygen-depleted ullage gases 96 (e.g., comprised of, e.g., nitrogen gasor other inert gas).

While it is possible to determine any chemical properties of ullagegases 96, in some examples it may be desirable to determine the presenceand/or amount of oxygen within ullage gases 96. In other examples, anamount of inert gas present within ullage gases 96 can be determined.Oxygen, for example, includes a series of absorbing bands and thus, thewavelengths of light beams 98 and 102 can be selected to be within theabsorbing bands of oxygen. Similarly, inert gases, such as nitrogen,include a series absorbing bands that may be different than theabsorbing bands of oxygen. In some examples, the wavelengths of lightbeams 98 and 102 can be selected to be within the absorbing bands of theinert gas. Absorption is distance dependent, so the distance that lightbeams 98 and 102 travel prior to arriving at imagers 90 and 102,respectively, must be known.

The light received at imagers 90 and 102 may be analyzed by controller28, for example, to determine an amount of absorption of the at leastone wavelength corresponding to a selected constituent of ullage gases96, such as oxygen, inert gas (e.g., nitrogen gas), or other selectedconstituent. For example, an intensity of light received by imagers 90and 102 may be known as a reference for when no oxygen is present. Thisreference may be compared to the active intensity of light received byimagers 90 and 102 to determine an amount of absorption of the at leastone wavelength. This amount of absorption along with the known distanceof travel for beams 98 and 102, may be utilized to determine a level ofa constituent, such as oxygen, inert gas, or other constituent withinullage gases 96. Such determined levels of constituent can be indicativeof an operational status of the inert gas generating system. Forinstance, a presence of oxygen or amount of oxygen that exceeds athreshold acceptability value can indicate a leak or other malfunctionof the inert gas generating system configured to generate theoxygen-depleted air.

Controller 28 can determine the operational status of the inert gasgenerating system based on the determined amount of absorption of the atleast one wavelength of one or more of light beams 98 and 102. Forinstance, controller 28 can determine an amount of a constituent, suchas oxygen, nitrogen, or other constituent of ullage gases 96 based onthe determined absorption. Controller 28 can determine the operationalstatus of the inert gas generating system corresponding to a failuremode of the inert gas generating system in response to determining thatthe amount of the constituent present in ullage gases 96 deviates fromone or more threshold acceptability criteria.

As one example, the one or more threshold acceptability criteria caninclude a threshold maximum limit corresponding to a maximum acceptableamount of the constituent (e.g., oxygen). Controller 28 can determinethat the amount of constituent present in ullage gases 96 deviates fromthe one or more threshold acceptability criteria in response todetermining that the amount of constituent present in ullage gases 96exceeds the threshold maximum limit corresponding to the maximumacceptable amount of the constituent. As another example, the one ormore threshold acceptability criteria can include a threshold minimumlimit corresponding to a minimum acceptable amount of the constituent(e.g., nitrogen gas or other inert gas). Controller 28 can determinethat the amount of constituent present in ullage gases 96 deviates fromthe one or more threshold acceptability criteria in response todetermining that the amount of constituent present in ullage gases 96 isless than the threshold minimum limit corresponding to the minimumacceptable amount of the constituent.

Accordingly, controller 28, implementing techniques of this disclosure,can determine an operational status of an inert gas generating systemconfigured to generate oxygen-depleted air for ullage of fuel tank 12.As such, the techniques described herein can increase awareness of theoperational status of the inert gas generating system, therebyincreasing system safety. While described with reference to imagers 92and 100, in other embodiments, a single photo sensor may also beutilized in place of imagers 92 and 100 to detect an intensity of lightfrom beams 98 and 102, respectively.

With continued reference to FIGS. 1-8B, FIGS. 9-13 are flow diagramsillustrating example operations for determining properties of a fueltank utilizing one or more image capture devices. For purposes ofclarity and ease of discussion, the example operations are describedbelow within the context of fuel tank monitoring system 10 and theembodiments described above.

FIG. 9 is a flow diagram illustrating example operations to produce afuel measurement value representing an amount of fuel contained in afuel tank based on reference image data and active image data of aninterior of the fuel tank. Reference image data can be generatedrepresenting a field of view of an interior of a fuel tank (Step 104).For example, imager 16 a can generate reference image 30 a representinga field of view of the interior of fuel tank 12. Active image data canbe generated representing the field of view of the interior of the fueltank when the fuel tank contains fuel (Step 106). For instance, imager16 a can generate active image 30 b representing the field of view ofthe interior of fuel tank 12 when fuel tank 12 contains fuel. A fuelmeasurement value can be produced representing an amount of fuelcontained in the fuel tank based on the reference image data and theactive image data (Step 108). As an example, controller 28 can produce afuel measurement value representing a volume of fuel contained in fueltank 12 based on image processing techniques to locate fuel level lines32 a-32 c and determine the volume of fuel based on a correspondence offuel level lines 32 a-32 c with one or more physical features of theinterior of fuel tank 12. An indication of the fuel measurement valuecan be provided as output (Step 110). For instance, controller 28 canoutput data including the fuel measurement value via one or morecommunication data buses.

FIG. 10 is a flow diagram illustrating example operations to produce afuel measurement value representing an amount of fuel contained in afuel tank disposed within a wing of an aircraft based on a determinedamount of wing bending of the wing. Image data can be generated of aninterior of a fuel tank disposed within a wing of an aircraft (Step112). For example, imager 50 can generate reference image data 53 a andactive image data 53 b of the interior of fuel tank 12 disposed withinwing 14 of an aircraft. An amount of wing bending of the wing of theaircraft can be determined based on the generated image data of theinterior of the fuel tank (Step 114). For instance, controller 28 candetermine distances 54 a-54 c between structural elements 52 a-52 d foreach of reference image data 53 a and active image data 53 b, and cancompare the distances 52 a-52 d between each of reference image data 53a and active image data 53 b to determine angle θ_(B) as the determinedamount of wing bending of wing 14. A fuel measurement value representingan amount of fuel contained in the fuel tank can be produced based onthe amount of wing bending of the wing of the aircraft (Step 116). As anexample, controller 28 can modify a shape of fuel tank 12 using a modelof the shape of fuel tank 12 based on the determined amount of wingbending, and can determine a fuel measurement value, such as a fuelvolume, a fuel mass, or other fuel measurement value based on themodified shape of fuel tank 12 within the model. An indication of thefuel measurement value can be output (Step 118). For instance,controller 28 can output data including the fuel measurement value viaone or more communication data buses.

FIG. 11 is a flow diagram illustrating example operations to produce afuel measurement value representing an amount of fuel contained in afuel tank based on three-dimensional image data of the interior of thefuel tank. An interior of a fuel tank can be illuminated with one ormore light pulses (Step 120). For example, time-of-flight imager 60 canemit light 64 using an integral or separate light source, such as adirectional laser light source. Reflected returns of the one or morelight pulses can be received at a light sensor array (Step 122). Forinstance, time-of-flight imager 60 can include a focal plane array thatprovides an image on a pixel-by-pixel basis. Light 64, after reflectionfrom fuel interface 62 and/or other physical features of the interior offuel tank 12 (e.g., spars 22, structural features 26, or other physicalfeatures) can be received at the focal plane array and analyzed by,e.g., controller 28. Three-dimensional (3D) image data of the interiorof the fuel tank can be produced based on the received reflected returns(Step 124). For example, controller 28 can determine the 3D image databy determining a time-of-flight of reflected returns of light 64 foreach pixel of the focal plane array. In certain examples, controller 28can determine the time-of-flight for each pixel based upon an intensityof each pixel (e.g., utilizing range gating techniques). In someexamples, controller 28 can determine the time-of-flight directly foreach pixel based on an elapsed time between emission of light 64 andreceipt of reflected returns of light 64 at each pixel of the focalplane array. In other examples, controller 28 can determine thetime-of-flight for each pixel based on a phase change between emittedlight 64 and reflected returns of light 64 at each pixel. A fuelmeasurement value representing an amount of fuel contained in the fueltank can be produced based on the three-dimensional image data (Step126). For instance, controller 28 can identify a correspondence (e.g., alocation of an intersection) between physical features of the interiorof fuel tank 12 and an interface of fuel and ullage within fuel tank 12based on the three-dimensional image data. Controller 28 can determine afuel measurement value, such as a volume of fuel contained in fuel tank12, based on the identified correspondence between the physical featuresof the interior of fuel tank 12 and the interface of fuel and ullagewithin fuel tank 12. An indication of the fuel measurement value can beoutput (Step 128). For instance, controller 28 can output data includingthe fuel measurement value via one or more communication data buses.

FIG. 12 is a flow diagram illustrating example operations to determine adensity of fuel contained in a fuel tank based on a determined index ofrefraction of the fuel. Directional light can be emitted from a lightsource through fuel contained in a fuel tank (Step 130). For example,light source 70 can emit directed beam of light 78 through fuelcontained in fuel tank 12. A refraction angle of the directional lightafter the directional light passes through an interface with the fuelcan be determined (Step 132). For instance, controller 28 can determineangle θ₂, which can be considered a refraction angle of beam 78 afterbeam 78 passes through the interface with the fuel (e.g., fuel interface74 separating ullage gases and fuel within fuel tank 12). An index ofrefraction of the fuel can be determined based on the determinedrefraction angle (Step 134). As an example, using both θ₁ and θ₂,controller 28 can utilize Snell's law to determine the index ofrefraction of the fuel. A density of the fuel can be determined based onthe determined index of refraction of the fuel (Step 136). For instance,controller 28 can determine the index of refraction based on angle θ₂ aswell as known properties of the fuel and a sensed temperature of thefuel (e.g., sensed via a thermal imager and/or temperature probedisposed within fuel tank 12). A fuel measurement value representing anamount of fuel contained in the fuel tank can be produced based on thedetermined density of the fuel (Step 138). For example, controller 28can determine a fuel measurement value representing a mass of fuelcontained in fuel tank 12 based on the determined density and adetermined volume of the fuel contained in fuel tank 12. An indicationof the fuel measurement value can be output. For instance, controller 28can output data including the fuel measurement value via one or morecommunication data buses.

FIG. 13 is a flow diagram illustrating example operations to determine achemical composition of a fuel tank ullage based on an amount ofabsorption of at least one wavelength of light transmitted through thefuel tank ullage. Light can be transmitted through a fuel tank ullage(Step 142). For example, light source 90 can emit light through adistance of ullage gases 96 of fuel tank 12. An amount of absorption ofat least one wavelength of the transmitted light can be determined (Step144). For instance, controller 28 can determine, based on an intensityof light received by imagers 90 and/or 102, an absorption of at leastone wavelength of the transmitted light. A chemical composition of thefuel tank ullage can be determined (Step 146). As an example, controller28 can determine a presence and/or amount of a constituent of ullagegases 96 (e.g., oxygen gas, nitrogen gas, or other constituent) based onthe amount of absorption of the at least one wavelength of thetransmitted light. Controller 28 can, in certain examples, determine anoperational status of an inert gas generating system configured togenerate oxygen-depleted air for the fuel tank ullage based on thedetermined amount of absorption of the at least one wavelength of thetransmitted light, such as an operational status corresponding to afailure mode of the inert gas generating system based on the presenceand/or amount of a constituent of ullage gases 96. For instance,controller 28 can determine the failure mode of the inert gas generatingsystem in response to determining that the amount of the constituentpresent in the ullage gases 96 deviates from one or more thresholdacceptability criteria, such as a maximum limit corresponding to amaximum acceptable amount of the constituent (e.g., a maximum amount ofoxygen gas), a minimum limit corresponding to a minimum acceptableamount of the constituent (e.g., a minimum amount of an inert gas, suchas nitrogen gas), or other threshold acceptability criteria. Controller28 can output, in some examples, the operational status of the inert gasgenerating system (e.g., an operational status corresponding to afailure mode and/or to a non-failure mode) to, e.g., one or moreconsuming systems, such as a data concentrator unit, an air conditioningsystem, cockpit displays, or other consuming system(s). Accordingly,controller 28 can help to increase system safety by determining and,e.g., outputting the operational status of the inert gas generatingsystem. In some examples, the determined chemical composition can beused to activate and/or deactivate the inert gas generating system. Forinstance, when controller 28 determines that an amount of a constituent,such as an inert gas constituent (e.g., nitrogen), satisfies thresholdcriteria, the inert gas generating system can be turned off or otherwisecease to provide inert gas for the fuel tank ullage. As such, techniquesof this disclosure can help to decrease an amount of power (e.g.,electrical power) consumed by an inert gas generating system, therebyincreasing system efficiency.

As described herein, a fuel tank monitoring system 10 can utilize imageprocessing techniques to determine properties of fuel tank 12, such asphysical features of an interior of fuel tank 12 (e.g., locations and/orphysical contours of spars 22, ribs 24, structural elements 26, or otherphysical features of the interior of fuel tank 12), a level and/orvolume of fuel within the interior of fuel tank 12, tilt of an aircraftthat includes fuel tank 12, an amount of bend of wing 14 of theaircraft, a density of the fuel within fuel tank 12, a chemicalcomposition of fluids within fuel tank 12 (e.g., fuel, gases within anullage of fuel tank 12, or other fluids within fuel tank 12), and/or atemperature of fluid(s) within fuel tank 12. The techniques can enablesuch properties to be determined without the use of in-tank capacitiveprobes, thereby helping to decrease a number of electrical componentsinstalled within an interior of fuel tank 12. Moreover, techniquesdescribed herein can decrease a total number of installed components,thereby helping to reduce installation and maintenance costs associatedwith operation of fuel tank monitoring system 10.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A method can include generating reference image data representing afield of view of an interior of a fuel tank and generating active imagedata representing the field of view of the interior of the fuel tankwhen the fuel tank contains fuel. The method can further includeproducing, by a processing device, a fuel measurement value representingan amount of fuel contained in the fuel tank based on the referenceimage data and the active image data, and outputting, by the processingdevice, an indication of the fuel measurement value.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

Generating the reference image data can include generating the referenceimage data when the fuel tank is empty of fuel.

Producing the fuel measurement value can include: identifying, based onthe reference image data, physical features of the interior of the fueltank; identifying, based on the active image data, a location of theinterior of the fuel tank corresponding to an interface of fuel andullage within the interior of the fuel tank; identifying a location ofthe interior of the fuel tank corresponding to an intersection of theinterface of fuel and ullage with one or more of the physical featuresof the interior of the fuel tank; and producing the fuel measurementvalue based on the location of the interior of the fuel tankcorresponding to the intersection of the interface of fuel and ullagewith the one or more of the physical features of the interior of thefuel tank.

Producing the fuel measurement value based on the location of theinterior of the fuel tank corresponding to the intersection of theinterface of fuel and ullage with the one or more of the physicalfeatures of the interior of the fuel tank can include determining, basedon a model of a shape of the fuel tank, a volume of fuel containedwithin the fuel tank.

The method can further include determining an adjusted shape of the fueltank based on the active image data using a model of the shape of thefuel tank. Producing the fuel measurement value can include determiningthe volume of fuel within the fuel tank based on the adjusted shape ofthe fuel tank.

The fuel tank can be disposed within a wing of the aircraft. Determiningthe adjusted shape of the fuel tank can include determining an amount ofwing bending of the wing of the aircraft.

Determining the amount of wing bending of the wing of the aircraft caninclude: determining a displacement of the one or more of the physicalfeatures between the reference image data and the active image data; anddetermining the amount of wing bending based on the determineddisplacement of the one or more of the physical features.

Generating the active image data representing the field of view of theinterior of the fuel tank can include generating first active image datarepresenting a first field of view of the interior of the fuel tank. Themethod can further include generating second active image datarepresenting a second field of view of the interior of the fuel tankwhen the fuel tank contains fuel. Producing the fuel measurement valuecan include producing the fuel measurement value representing the amountof fuel contained in the fuel tank based on the reference image data andthe first and second active image data.

The first field of view of the interior of the fuel tank can include anupper portion of the interior of the fuel tank. The second field of viewof the interior of the fuel tank can include a lower portion of theinterior of the fuel tank. Generating the first active image data caninclude generating the first active image data using an image capturingdevice disposed at the lower portion of the interior of the fuel tank.Generating the second active image data can include generating thesecond active image data using an image capturing device disposed at theupper portion of the interior of the fuel tank.

Generating the first active image data representing the first field ofview including the upper portion of the interior of the fuel tank caninclude illuminating the interior of the fuel tank using a light sourcedisposed at the upper portion of the interior of the fuel tank.

Generating the first active image data representing the first field ofview including the upper portion of the interior of the fuel tank caninclude illuminating the interior of the fuel tank using a light sourcedisposed at the lower portion of the interior of the fuel tank.

Generating the second active image data representing the second field ofview including the lower portion of the interior of the fuel tank caninclude illuminating the interior of the fuel tank using a light sourcedisposed at the lower portion of the interior of the fuel tank.

Generating the second active image data representing the second field ofview including the lower portion of the interior of the fuel tank caninclude illuminating the interior of the fuel tank using a light sourcedisposed at the upper portion of the interior of the fuel tank.

Generating the active image data can include generating the active imagedata using one or more image capturing devices disposed within aninterior of the fuel tank.

Generating the active image data can include generating the active imagedata using one or more image capturing devices disposed external to theinterior of the fuel tank.

A system can include one or more image capturing devices, at least oneprocess, and computer-readable memory. The one or more image capturingdevices can be located to: generate reference image data representing ofan interior of a fuel tank; and generate active image data of theinterior of the fuel tank when the fuel tank contains fuel. Thecomputer-readable memory can be encoded with instructions that, whenexecuted by the at least one processor, cause the system to: produce afuel measurement value representing an amount of fuel contained in thefuel tank based on the reference image data and the active image data;and output an indication of the fuel measurement value.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value by at least causing the system to:identify, based on the reference image data, physical features of theinterior of the fuel tank; identify, based on the active image data, alocation of the interior of the fuel tank corresponding to an interfaceof fuel and ullage within the interior of the fuel tank; identify alocation of the interior of the fuel tank corresponding to anintersection of the interface of fuel and ullage with one or more of thephysical features of the interior of the fuel tank; and produce the fuelmeasurement value based on the location of the interior of the fuel tankcorresponding to the intersection of the interface of fuel and ullagewith the one or more of the physical features of the interior of thefuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value based on the location of the interiorof the fuel tank corresponding to the intersection of the interface offuel and ullage with the one or more of the physical features of theinterior of the fuel tank by at least causing the system to determine,based on a model of a shape of the fuel tank, a volume of fuel containedwithin the fuel tank.

The fuel tank can be disposed within a wing of an aircraft. Thecomputer-readable memory can be further encoded with instructions that,when executed by the at least one processor, cause the system to:determine an amount of wing bending of the wing of the aircraft;determine an adjusted shape of the fuel tank based on the determinedamount of wing bending using a model of the shape of the fuel tank; andproduce the fuel measurement value by at least determining the volume offuel within the fuel tank based on the adjusted shape of the fuel tank.

The active image data of the interior of the fuel tank can include firstactive image data representing a first field of view of the interior ofthe fuel tank. The one or more image capturing devices can be furtherlocated to generate second active image data of the interior of the fueltank when the fuel tank contains fuel. The computer-readable memory canbe further encoded with instructions that, when executed by the at leastone processor, cause the system to produce the fuel measurement value byat least causing the system to produce the fuel measurement value basedon the reference image data and the first and second active image data.

The one or more image capturing devices can include: a first imagecapturing device located at a lower portion of the interior of the fueltank to generate the first active image data representing the firstfield of view of the interior of the fuel tank, wherein the first fieldof view includes an upper portion of the interior of the fuel tank; anda second image capturing device located at the upper portion of theinterior of the fuel tank to generate the second active image datarepresenting the second field of view of the interior of the fuel tank,wherein the second field of view includes the lower portion of theinterior of the fuel tank.

A method can include generating image data of an interior of a fuel tankdisposed within a wing of an aircraft, and determining, by a processingdevice, an amount of wing bending of the wing of the aircraft based onthe generated image data of the interior of the fuel tank. The methodcan further include producing, by the processing device, a fuelmeasurement value representing an amount of fuel contained in the fueltank based on the amount of wing bending of the wing of the aircraft,and outputting, by the processing device, an indication of the fuelmeasurement value.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

Generating the image data of the interior of the fuel tank can includegenerating active image data when the fuel tank contains fuel. Themethod can further include generating reference image data of theinterior of the fuel tank. Determining the amount of wing bending of thewing of the aircraft can include determining the amount of wing bendingof the wing of the aircraft based on the active image data and thereference image data.

Determining the amount of wing bending can include: determining, basedon the active image data and the reference image data, a displacement ofone or more physical features of the interior of the fuel tank; anddetermining the amount of wing bending based on the determineddisplacement of the one or more physical features.

Producing the fuel measurement value can include: adjusting a shape ofthe fuel tank based on the determined amount of wing bending using amodel of the shape of the fuel tank; and producing the fuel measurementvalue based on the adjusted shape of the fuel tank.

Producing the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the adjusted shape of the fuel tankcan include: identifying, based on the generated image data, a locationof the interior of the fuel tank corresponding to an interface of fueland ullage within the interior of the fuel tank; identifying a locationof an intersection of the interface of fuel and ullage with one or morephysical features identified in the model of the adjusted shape of thefuel tank; and determining a volume of fuel contained within the fueltank based on the identified location of the intersection of theinterface of fuel and ullage with the one or more physical featuresidentified in the model of the adjusted shape of the fuel tank.

Generating the image data of the interior of the fuel tank can includegenerating the image data using one or more image capturing deviceslocated to generate the image data of the interior of the fuel tank.

The one or more image capturing devices can include a plurality of imagecapturing devices disposed at a plurality of locations to include aplurality of fields of view of the interior of the fuel tank.

A device can include at least one processor and computer-readablememory. The computer-readable memory can be encoded with instructionsthat, when executed by the at least one processor, cause the device to:receive image data of an interior of a fuel tank disposed within a wingof an aircraft; determine an amount of wing bending of the wing of theaircraft based on the received image data of the interior of the fueltank; produce a fuel measurement value representing an amount of fuelcontained in the fuel tank based on the amount of wing bending of thewing of the aircraft; and output the fuel measurement value.

The device of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The received image data of the interior of the fuel tank disposed withinthe wing of the aircraft can include active image data generated whenthe fuel tank contains fuel. The computer-readable memory can be furtherencoded with instructions that, when executed by the at least oneprocessor, cause the device to: receive reference image data of theinterior of the fuel tank; and determine the amount of wing bending ofthe wing of the aircraft by at least determining the amount of wingbending of the wing of the aircraft based on the active image data andthe reference image data.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device todetermine the amount of wing bending by at least causing the device to:determine, based on the active image data and the reference image data,a displacement of one or more physical features of the interior of thefuel tank; and determine the amount of wing bending based on thedetermined displacement of the one or more physical features.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device toproduce the fuel measurement value by at least causing the device to:adjust a shape of the fuel tank based on the determined amount of wingbending using a model of the shape of the fuel tank; and produce thefuel measurement value based on the adjusted shape of the fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the adjusted shape of the fuel tankby at least causing the device to: identify, based on the generatedimage data, a location of the interior of the fuel tank corresponding toan interface of fuel and ullage within the interior of the fuel tank;identify a location of an intersection of the interface of fuel andullage with one or more physical features identified in the model of theadjusted shape of the fuel tank; and determine a volume of fuelcontained within the fuel tank based on the identified location of theintersection of the interface of fuel and ullage with the one or morephysical features identified in the model of the adjusted shape of thefuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device toreceive the image data of the interior of the fuel tank by at leastcausing the device to receive the image data from one or more imagecapturing devices located to generate the image data of the interior ofthe fuel tank.

A system can include one or more image capturing devices, at least oneprocessor, and computer-readable memory. The one or more image capturingdevices can be located to generate image data of an interior of a fueltank disposed within a wing of an aircraft. The computer-readable memorycan be encoded with instructions that, when executed by the at least oneprocessor, cause the system to: generate, using the one or more imagecapturing devices, the image data of the interior of the fuel tankdisposed within the wing of the aircraft; determine and amount of wingbending of the wing of the aircraft based on the generated image data ofthe interior of the fuel tank; produce a fuel measurement valuerepresenting an amount of fuel contained in the fuel tank based on theamount of wing bending of the wing of the aircraft; and output the fuelmeasurement value.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The generated image data of the interior of the fuel tank disposedwithin the wing of the aircraft can include active image data generatedwhen the fuel tank contains fuel. The computer-readable memory can befurther encoded with instructions that, when executed by the at leastone processor, cause the system to: generate, using the one or moreimage capturing devices, reference image data of the interior of thefuel tank; and determine the amount of wing bending of the wing of theaircraft by at least determining the amount of wing bending of the wingof the aircraft based on the active image data and the reference imagedata.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system todetermine the amount of wing bending by at least causing the system to:determine, based on the active image data and the reference image data,a displacement of one or more physical features of the interior of thefuel tank; and determine the amount of wing bending based on thedetermined displacement of the one or more physical features.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value by at least causing the system to:adjust a shape of the fuel tank based on the determined amount of wingbending using a model of the shape of the fuel tank; and produce thefuel measurement value representing the amount of fuel contained in thefuel tank based on the adjusted shape of the fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the adjusted shape of the fuel tankby at least causing the system to: identify, based on the generatedimage data, a location of the interior of the fuel tank corresponding toan interface of fuel and ullage within the interior of the fuel tank;identify a location of an intersection of the interface of fuel andullage with one or more physical features identified in the model of theadjusted shape of the fuel tank; and determine a volume of fuelcontained within the fuel tank based on the identified location of theintersection of the interface of fuel and ullage with the one or morephysical features identified in the model of the adjusted shape of thefuel tank.

The one or more image capturing devices can include a plurality of imagecapturing devices disposed at a plurality of locations to include aplurality of fields of view of the interior of the fuel tank.

An aggregate of the plurality of fields of view of the interior of thefuel tank comprise an entirety of the interior of the fuel tank.

A method can include illuminating an interior of a fuel tank with one ormore light pulses, receiving reflected returns of the one or more lightpulses at a light sensor array, and producing, by a processing device,three-dimensional image data of the interior of the fuel tank based onthe received reflected returns. The method can further includeproducing, by the processing device, a fuel measurement valuerepresenting an amount of fuel contained in the fuel tank based on thethree-dimensional image data, and outputting, by the processing device,an indication of the fuel measurement value.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

Producing the three-dimensional image data of the interior of the fueltank based on the received reflected returns can include associatingeach pixel of a plurality of pixels of the three-dimensional image datawith an intensity and a distance traveled of a received reflected returnassociated with the pixel.

Associating each pixel of the plurality of pixels of thethree-dimensional image data with the distance traveled of the receivedreflected return associated with the pixel can include determining thedistance traveled of the received reflected return based on atime-of-flight of the received reflected return.

Associating each pixel of the plurality of pixels of thethree-dimensional image data with the distance traveled of the receivedreflected return associated with the pixel can include determining thedistance traveled of the received reflected return based on aphase-shift of the received reflected return.

Producing the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the three-dimensional image data caninclude: identifying, based on the three-dimensional image data,physical features of the interior of the fuel tank; identifying, basedon the three-dimensional image data, a location of the interior of thefuel tank corresponding to an interface of fuel and ullage within theinterior of the fuel tank; and producing the fuel measurement valuebased on the location of the interior of the fuel tank corresponding tothe interface of fuel and ullage within the interior of the fuel tank.

Producing the fuel measurement value based on the location of theinterior of the fuel tank corresponding to the interface of fuel andullage within the interior of the fuel tank can include identifying alocation of the interior of the fuel tank corresponding to anintersection of the interface of fuel and ullage with one or more of thephysical features of the interior of the fuel tank.

Producing the fuel measurement value based on the location of theinterior of the fuel tank corresponding to the interface of fuel andullage within the interior of the fuel tank can include determining,based on a model of a shape of the fuel tank, a volume of fuel containedwithin the fuel tank.

The fuel tank can be disposed within a wing of an aircraft. The methodcan further include: determining an amount of wing bending of the wingof the aircraft; and determining an adjusted shape of the fuel tankbased on the determined amount of wing bending using a model of theshape of the fuel tank. Producing the fuel measurement value can includedetermining the volume of fuel within the fuel tank based on theadjusted shape of the fuel tank.

Determining the amount of wing bending of the wing of the aircraft caninclude determining a displacement of the one or more of the physicalfeatures between a reference location of the one or more of the physicalfeatures and a location of the one or more physical features within thethree-dimensional image data.

The method can further include determining the reference location of theone or more of the physical features based on the model of the shape ofthe fuel tank.

A system can include a light source, a light sensor array, at least oneprocessor, and computer-readable memory. The computer-readable memorycan be encoded with instructions that, when executed by the at least oneprocessor, cause the system to: illuminate an interior of a fuel tankwith one or more light pulses emitted from the light source; producethree-dimensional image data of the interior of the fuel tank based onreflected returns of the one or more light pulses received at the lightsensor array; produce a fuel measurement value representing an amount offuel contained in the fuel tank based on the three-dimensional imagedata; and output an indication of the fuel measurement value.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the three-dimensional image data of the interior of the fueltank by at least causing the system to associate each pixel of aplurality of pixels of the three-dimensional image data with anintensity and a distance traveled of a received reflected returnassociated with the pixel.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toassociate each pixel of the plurality of pixels of the three-dimensionalimage data with the distance traveled of the received reflected returnassociated with the pixel by at least causing the system to determinethe distance traveled of the received reflected return based on atime-of-flight of the received reflected return.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toassociate each pixel of the plurality of pixels of the three-dimensionalimage data with the distance traveled of the received reflected returnassociated with the pixel by at least causing the system to determinethe distance traveled of the received reflected return based on aphase-shift of the received reflected return.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the three-dimensional image data byat least causing the system to: identify, based on the three-dimensionalimage data, physical features of the interior of the fuel tank;identify, based on the three-dimensional image data, a location of theinterior of the fuel tank corresponding to an interface of fuel andullage within the interior of the fuel tank; and produce the fuelmeasurement value based on the location of the interior of the fuel tankcorresponding to the interface of fuel and ullage within the interior ofthe fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value based on the location of the interiorof the fuel tank corresponding to the interface of fuel and ullagewithin the interior of the fuel tank by at least causing the system toidentify a location of the interior of the fuel tank corresponding to anintersection of the interface of fuel and ullage with one or more of thephysical features of the interior of the fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value based on the location of the interiorof the fuel tank corresponding to the interface of fuel and ullagewithin the interior of the fuel tank by at least causing the system todetermine, based on a model of a shape of the fuel tank, a volume offuel contained within the fuel tank.

The fuel tank can be disposed within a wing of an aircraft. Thecomputer-readable memory can be further encoded with instructions that,when executed by the at least one processor, cause the system to:determine an amount of wing bending of the wing of the aircraft;determine an adjusted shape of the fuel tank based on the determinedamount of wing bending using a model of the shape of the fuel tank; andproduce the fuel measurement value by determining the volume of fuelwithin the fuel tank based on the adjusted shape of the fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system todetermine the amount of wing bending of the wing of the aircraft by atleast causing the system to determine a displacement of the one or moreof the physical features between a reference location of the one or moreof the physical features and a location of the one or more physicalfeatures within the three-dimensional image data.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system todetermine the reference location of the one or more of the physicalfeatures based on the model of the shape of the fuel tank.

A device can include at least one processor and computer-readablememory. The computer-readable memory can be encoded with instructionsthat, when executed by the at least one processor, cause the device to:produce three-dimensional image data of an interior of a fuel tank basedon received reflected returns of one or more light pulses used toilluminate the interior of the fuel tank; produce a fuel measurementvalue representing an amount of fuel contained in the fuel tank based onthe three-dimensional image data; and output an indication of the fuelmeasurement value.

The device of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the three-dimensional image data byat least causing the system to: identify, based on the three-dimensionalimage data, physical features of the interior of the fuel tank;identify, based on the three-dimensional image data, a location of theinterior of the fuel tank corresponding to an interface of fuel andullage within the interior of the fuel tank; and produce the fuelmeasurement value based on the location of the interior of the fuel tankcorresponding to the interface of fuel and ullage within the interior ofthe fuel tank.

A method can include emitting, from a light source, directional lightthrough fuel contained in a fuel tank, determining a refraction angle ofthe directional light after the directional light passes through aninterface with the fuel, and determining, by a processing device, anindex of refraction of the fuel based on the determined refractionangle. The method can further include determining, by the processingdevice, a density of the fuel based on the determined index ofrefraction of the fuel.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The method can further include producing, by the processing device, afuel measurement value representing an amount of fuel contained in thefuel tank based on the determined density of the fuel, and outputting,by the processing device, an indication of the fuel measurement value.

Producing the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the determined density of the fuelcan include determining a mass of the fuel contained in the fuel tankbased on a determined volume of the fuel contained in the fuel tank andthe determined density of the fuel.

Determining the refraction angle of the directional light can includeidentifying, using an image capturing device, a location of an interiorof the fuel tank intersected by the directional light after thedirectional light passes through the interface with the fuel.

Determining the refraction angle of the directional light can furtherinclude determining a distance between the location of the interior ofthe fuel tank intersected by the directional light and a location of theinterior of the fuel tank corresponding to non-refraction of thedirectional light.

The method can further include measuring, using a thermal imagingdevice, a temperature of the fuel. Determining the density of the fuelbased on the determined index of refraction of the fuel can includedetermining the density of the fuel based on the determined index ofrefraction of the fuel and the measured temperature of the fuel.

The light source can include a laser light source.

The interface with the fuel can include an interface between the fueland ullage gas of the fuel tank.

A system can include a light source, at least one processor, andcomputer-readable memory. The light source can be configured to emitdirectional light. The computer-readable memory can be encoded withinstructions that, when executed by the at least one processor, causethe system to: emit the directional light from the light source throughfuel contained in a fuel tank; determine a refraction angle of thedirectional light after the directional light passes through aninterface with the fuel; determine an index of refraction of the fuelbased on the measured refraction angle; and determine a density of thefuel based on the determined index of refraction of the fuel.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system to:produce a fuel measurement value representing an amount of fuelcontained in the fuel tank based on the determined density of the fuel;and output an indication of the fuel measurement value.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the determined density of the fuelby at least causing the system to determine a mass of the fuel containedin the fuel tank based on a determined volume of the fuel contained inthe fuel tank and the determined density of the fuel.

The system can further include an image capturing device located toinclude a field of view of an interior of the fuel tank. Thecomputer-readable memory can be further encoded with instructions that,when executed by the at least one processor, cause the system todetermine the refraction angle of the directional light by at leastcausing the system to: generate image data of the interior of the fueltank using the image capturing device; and identify, using the imagedata, a location of the interior of the fuel tank intersected by thedirectional light after the directional light passes through theinterface with the fuel.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system todetermine the refraction angle of the directional light by at leastcausing the system to determine, using the image data, a distancebetween the location of the interior of the fuel tank intersected by thedirectional light and a location of the interior of the fuel tankcorresponding to non-refraction of the directional light.

The system can further include a thermal imaging device located toinclude a field of view of an interior of the fuel tank. Thecomputer-readable memory can be further encoded with instructions that,when executed by the at least one processor, cause the system todetermine the density of the fuel based on the determined index ofrefraction of the fuel by at least causing the system to determine thedensity of the fuel based on the determined index of refraction of thefuel and a temperature of the fuel measured using the thermal imagingdevice.

The light source can include a laser light source.

The interface with the fuel can include an interface between the fueland ullage gas of the fuel tank.

A device can include at least one processor and computer-readablememory. The computer-readable memory can be encoded with instructionsthat, when executed by the at least one processor, cause the device to:determine a refraction angle of directional light emitted from a lightsource through fuel contained in a fuel tank after the directional lightpasses through an interface with the fuel; determine an index ofrefraction of the fuel based on the measured refraction angle; anddetermine a density of the fuel based on the determined index ofrefraction of the fuel.

The device of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device to:produce a fuel measurement value representing an amount of fuelcontained in the fuel tank based on the determined density of the fuel;and output an indication of the fuel measurement value

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device todetermine the refraction angle of the directional light by at leastcausing the device to identify, using the image data generated by animage capturing device located to include a field of view of theinterior of the fuel tank, a location of the interior of the fuel tankintersected by the directional light after the directional light passesthrough the interface with the fuel.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device todetermine the refraction angle of the directional light by at leastcausing the device to determine, using the image data, a distancebetween the location of the interior of the fuel tank intersected by thedirectional light and a location of the interior of the fuel tankcorresponding to non-refraction of the directional light.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device todetermine the density of the fuel based on the determined index ofrefraction of the fuel by at least causing the device to determine thedensity of the fuel based on the determined index of refraction of thefuel and a temperature of the fuel measured using a thermal imagingdevice.

The light source can include a laser light source. The interface withthe fuel can include an interface between the fuel and ullage gas of thefuel tank.

A method can include transmitting, from a light source, light through afuel tank ullage, and determining, by a processing device, an amount ofabsorption of at least one wavelength of the transmitted light. Themethod can further include determining, by the processing device basedon the amount of absorption of the at least one wavelength of thetransmitted light, a chemical composition of the fuel tank ullage.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

Determining the amount of absorption of the at least one wavelength ofthe transmitted light can include: receiving the transmitted light at animage sensing device after the light is transmitted through the fueltank ullage; measuring an intensity of the at least one wavelengthreceived at the image sensing device; measuring an intensity of the atleast one wavelength transmitted by the light source; and determiningthe amount of absorption of the at least one wavelength based on achange between the measured intensity of the at least one wavelengthtransmitted by the light source and the measured intensity of the atleast one wavelength received at the image sensing device.

The image sensing device can be disposed at a location that is remotefrom the light source.

The image sensing device can be co-located with the light source.Receiving the transmitted light at the image sensing device after thelight is transmitted through the fuel tank ullage can include receivinga reflection of the transmitted light after the transmitted light isreflected from a location that is a distance from the light source.

Determining the chemical composition of the fuel tank ullage can includedetermining presence of a constituent in the fuel tank ullage based onthe determined amount of absorption of the at least one wavelength. Themethod can further include determining, based on the determined presenceof the constituent in the fuel tank ullage, an operational status of aninert gas generating system configured to produce oxygen-depleted airfor the fuel tank ullage.

The at least one wavelength of the transmitted light can include anabsorption wavelength of oxygen. Determining the presence of theconstituent in the fuel tank ullage based on the determined amount ofabsorption of the at least one wavelength can include determining thepresence of oxygen based on the determined amount of absorption of theabsorption wavelength of oxygen.

Determining the presence of the constituent in the fuel tank ullagebased on the determined amount of absorption of the at least onewavelength can include determining an amount of the constituent presentin the fuel tank ullage based on the determined amount of absorption ofthe at least one wavelength. Determining the operational status of theinert gas generating system can include determining the operationalstatus corresponding to a failure mode of the inert gas generatingsystem in response to determining that the amount of the constituentpresent in the fuel tank ullage deviates from one or more thresholdacceptability criteria.

The one or more threshold acceptability criteria can include a thresholdmaximum limit corresponding to a maximum acceptable amount of theconstituent. Determining that the amount of the constituent present inthe fuel tank ullage deviates from the one or more thresholdacceptability criteria can include determining that the amount of theconstituent present in the fuel tank ullage exceeds the thresholdmaximum limit corresponding to the maximum acceptable amount of theconstituent.

The one or more threshold acceptability criteria can include a thresholdminimum limit corresponding to a minimum acceptable amount of theconstituent. Determining that the amount of the constituent present inthe fuel tank ullage deviates from the one or more thresholdacceptability criteria can include determining that the amount of theconstituent present in the fuel tank ullage is less than the thresholdminimum limit corresponding to the minimum acceptable amount of theconstituent.

A system can include a light source, at least one processor, andcomputer-readable memory. The light source can be located to transmitlight through a fuel tank ullage. The computer-readable memory can beencoded with instructions that, when executed by the at least oneprocessor, cause the system to: transmit the light from the light sourcethrough the fuel tank ullage; determine an amount of absorption of atleast one wavelength of the transmitted light; and determine, based onthe amount of absorption of the at least one wavelength of thetransmitted light, a chemical composition of the fuel tank ullage.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The system can further include an image sensing device located toreceive the transmitted light after the light is transmitted through thefuel tank ullage. The computer-readable memory can be further encodedwith instructions that, when executed by the at least one processor,cause the system to determine the amount of absorption of the at leastone wavelength of the transmitted light by at least causing the systemto: measure an intensity of the at least one wavelength received at theimage sensing device; measure an intensity of the at least onewavelength transmitted by the light source; and determine the amount ofabsorption of the at least one wavelength based on a change between themeasured intensity of the at least one wavelength transmitted by thelight source and the measured intensity of the at least one wavelengthreceived at the image sensing device.

The image sensing device can be disposed at a location that is remotefrom the light source.

The image sensing device can be co-located with the light source toreceive a reflection of the transmitted light after the transmittedlight is reflected from a location that is a distance from the lightsource.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system to:determine the chemical composition of the fuel tank ullage by at leastcausing the system to determine presence of a constituent in the fueltank ullage based on the determined amount of absorption of the at leastone wavelength; and determine, based on the determined presence of theconstituent in the fuel tank ullage, an operational status of an inertgas generating system configured to produce oxygen-depleted air for thefuel tank ullage.

The at least one wavelength of the transmitted light can include anabsorption wavelength of oxygen. The computer-readable memory can befurther encoded with instructions that, when executed by the at leastone processor, cause the system to determine the presence of theconstituent in the fuel tank ullage based on the determined amount ofabsorption of the at least one wavelength by at least causing the systemto determine the presence of oxygen based on the determined amount ofabsorption of the absorption wavelength of oxygen.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system to:determine the presence of the constituent in the fuel tank ullage by atleast causing the system to determine an amount of the constituentpresent in the fuel tank ullage based on the determined amount ofabsorption of the at least one wavelength; and determine the operationalstatus of the inert gas generating system by at least causing the systemto determine the operational status corresponding to a failure mode ofthe inert gas generating system in response to determining that theamount of the constituent present in the fuel tank ullage deviates fromone or more threshold acceptability criteria.

The one or more threshold acceptability criteria can include a thresholdmaximum limit corresponding to a maximum acceptable amount of theconstituent. The computer-readable memory can be further encoded withinstructions that, when executed by the at least one processor, causethe system to determine that the amount of the constituent present inthe fuel tank ullage deviates from the one or more thresholdacceptability criteria by at least causing the system to determine thatthe amount of the constituent present in the fuel tank ullage exceedsthe threshold maximum limit corresponding to the maximum acceptableamount of the constituent.

The one or more threshold acceptability criteria can include a thresholdminimum limit corresponding to a minimum acceptable amount of theconstituent. The computer-readable memory can be further encoded withinstructions that, when executed by the at least one processor, causethe system to determine that the amount of the constituent present inthe fuel tank ullage deviates from the one or more thresholdacceptability criteria by at least causing the system to determine thatthe amount of the constituent present in the fuel tank ullage is lessthan the threshold minimum limit corresponding to the minimum acceptableamount of the constituent.

A device can include at least one processor and computer-readablememory. The computer-readable memory can be encoded with instructionsthat, when executed by the at least one processor, cause the device to:determine an amount of absorption of at least one wavelength of lighttransmitted from a light source through a fuel tank ullage; anddetermine, based on the amount of absorption of the at least onewavelength of the transmitted light, a chemical composition of the fueltank ullage.

The device of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the device todetermine the amount of absorption of the at least one wavelength of thetransmitted light by at least causing the device to determine the amountof absorption of the at least one wavelength of the transmitted lightbased on a change between a measured intensity of the at least onewavelength transmitted by the light source and a measured intensity ofthe at least one wavelength received at an image sensing device afterthe light is transmitted through a distance of the fuel tank ullage.

A method can include generating first image data representing a firstfield of view of an interior of a fuel tank using a first imagecapturing device disposed at an upper portion of the interior of thefuel tank, and generating second image data representing a second fieldof view of the interior of the fuel tank using a second image capturingdevice disposed at a lower portion of the interior of the fuel tank. Themethod can further include producing, by a processing device, a fuelmeasurement value representing an amount of fuel contained in the fueltank based on the first image data and the second image data, andoutputting, by the processing device, an indication of the fuelmeasurement value.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The first field of view of the interior of the fuel tank can include thelower portion of the interior of the fuel tank. The second field of viewof the interior of the fuel tank can include the upper portion of theinterior of the fuel tank.

Generating the first image data can include illuminating the first fieldof view using a light source disposed at the upper portion of theinterior of the fuel tank.

Generating the first image data can include illuminating the first fieldof view using a light source disposed at the lower portion of theinterior of the fuel tank.

Generating the second image data representing the second field of viewincluding the upper portion of the interior of the fuel tank can includeilluminating the second field of view using a light source disposed atthe lower portion of the interior of the fuel tank.

Generating the second image data representing the second field of viewincluding the upper portion of the interior of the fuel tank can includeilluminating the second field of view using a light source disposed atthe upper portion of the interior of the fuel tank.

Generating the first image data representing the first field of viewincluding the lower portion of the interior of the fuel tank andgenerating the second image data representing the second field of viewincluding the lower portion of the interior of the fuel tank can includegenerating the first image data and the second image data when aninterface between fuel contained in the fuel tank and ullage of the fueltank separates the first image capturing device and the second imagecapturing device.

Producing the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the first image data and the secondimage data can include identifying, based on the first image data andthe second image data, a location of the interior of the fuel tank thatintersects the interface between the fuel contained in the fuel tank andthe ullage of the fuel tank.

Producing the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the first image data and the secondimage data further can include determining, based on a model of a shapeof the fuel tank, a volume of fuel beneath the location of the interiorof the fuel tank that intersects the interface between the fuelcontained in the fuel tank and the ullage of the fuel tank.

A system can include a first image capturing device, a second imagecapturing device, at least one processor, and computer-readable memory.The first image capturing device can be disposed at an upper portion ofan interior of a fuel tank. The second image capturing device can bedisposed at a lower portion of the interior of the fuel tank. Thecomputer-readable memory can be encoded with instructions that, whenexecuted by the at least one processor, cause the system to: generate,using the first image capturing device, first image data representing afirst field of view of the interior of a fuel tank; generate, using thesecond image capturing device, second image data representing a secondfield of view of the interior of the fuel tank; produce a fuelmeasurement value representing an amount of fuel contained in the fueltank based on the first image data and the second image data; and outputan indication of the fuel measurement value.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The first field of view of the interior of the fuel tank can include thelower portion of the interior of the fuel tank. The second field of viewof the interior of the fuel tank can include the upper portion of theinterior of the fuel tank.

The system can further include a light source disposed at the upperportion of the interior of the fuel tank. The computer-readable memorycan be further encoded with instructions that, when executed by the atleast one processor, cause the system to generate the first image datarepresenting the first field of view including the lower portion of theinterior of the fuel tank by at least causing the system to illuminatethe first field of view using the light source disposed at the upperportion of the interior of the fuel tank.

The system can further include a light source disposed at the lowerportion of the interior of the fuel tank. The computer-readable memorycan be further encoded with instructions that, when executed by the atleast one processor, cause the system to generate the first image datarepresenting the first field of view including the lower portion of theinterior of the fuel tank by at least causing the system to illuminatethe first field of view using the light source disposed at the lowerportion of the interior of the fuel tank.

The system can further include a light source disposed at the lowerportion of the interior of the fuel tank. The computer-readable memorycan be further encoded with instructions that, when executed by the atleast one processor, cause the system to generate the second image datarepresenting the second field of view including the upper portion of theinterior of the fuel tank by at least causing the system to illuminatethe second field of view using the light source disposed at the lowerportion of the interior of the fuel tank.

The system can further include a light source disposed at the upperportion of the interior of the fuel tank. The computer-readable memorycan be further encoded with instructions that, when executed by the atleast one processor, cause the system to generate the second image datarepresenting the second field of view including the upper portion of theinterior of the fuel tank by at least causing the system to illuminatethe second field of view using the light source disposed at the upperportion of the interior of the fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system togenerate the first image data representing the first field of viewincluding the lower portion of the interior of the fuel tank andgenerate the second image data representing the second field of viewincluding the lower portion of the interior of the fuel tank by at leastcausing the system to generate the first image data and the second imagedata when an interface between fuel contained in the fuel tank andullage of the fuel tank separates the first image capturing device andthe second image capturing device.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the first image data and the secondimage data by at least causing the system to identify, based on thefirst image data and the second image data, a location of the interiorof the fuel tank corresponding to the interface between the fuelcontained in the fuel tank and the ullage of the fuel tank.

The computer-readable memory can be further encoded with instructionsthat, when executed by the at least one processor, cause the system toproduce the fuel measurement value representing the amount of fuelcontained in the fuel tank based on the first image data and the secondimage data by at least causing the system to determine, based on a modelof a shape of the fuel tank, a volume of fuel beneath the location ofthe interior of the fuel tank that corresponds to the interface betweenthe fuel contained in the fuel tank and the ullage of the fuel tank.

A device can include at least one processor and computer-readablememory. The computer-readable memory can be encoded with instructionsthat, when executed by the at least one processor, cause the device to:produce a fuel measurement value representing an amount of fuelcontained in a fuel tank based on first image data representing a firstfield of view of an interior of the fuel tank generated by a first imagecapturing device disposed at an upper portion of the interior of thefuel tank and second image data representing a second field of view ofthe interior of the fuel tank generated by a second image capturingdevice disposed at a lower portion of the interior of the fuel tank; andoutput an indication of the fuel measurement value.

The device of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations, operations, and/or additional components:

The first field of view of the interior of the fuel tank can include thelower portion of the interior of the fuel tank. The second field of viewof the interior of the fuel tank can include the upper portion of theinterior of the fuel tank.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A method comprising: generating image data of an interior of a fueltank disposed within a wing of an aircraft; determining, by a processingdevice, an amount of wing bending of the wing of the aircraft based onthe generated image data of the interior of the fuel tank; producing, bythe processing device, a fuel measurement value representing an amountof fuel contained in the fuel tank based on the amount of wing bendingof the wing of the aircraft; and outputting, by the processing device,an indication of the fuel measurement value.
 2. The method of claim 1,wherein generating the image data of the interior of the fuel tankcomprises generating active image data when the fuel tank contains fuel,the method further comprising: generating reference image data of theinterior of the fuel tank; wherein determining the amount of wingbending of the wing of the aircraft comprises determining the amount ofwing bending of the wing of the aircraft based on the active image dataand the reference image data.
 3. The method of claim 2, whereindetermining the amount of wing bending comprises: determining, based onthe active image data and the reference image data, a displacement ofone or more physical features of the interior of the fuel tank; anddetermining the amount of wing bending based on the determineddisplacement of the one or more physical features.
 4. The method ofclaim 1, wherein producing the fuel measurement value comprises:adjusting a model of a shape of the fuel tank based on the determinedamount of wing bending; and producing the fuel measurement value basedon the adjusted model of the shape of the fuel tank.
 5. The method ofclaim 4, wherein producing the fuel measurement value representing theamount of fuel contained in the fuel tank based on the adjusted model ofthe shape of the fuel tank comprises: identifying, based on thegenerated image data, a location of the interior of the fuel tankcorresponding to an interface of fuel and ullage within the interior ofthe fuel tank; identifying a location of an intersection of theinterface of fuel and ullage with one or more physical featuresidentified in the adjusted model of the fuel tank; and determining avolume of fuel contained within the fuel tank based on the identifiedlocation of the intersection of the interface of fuel and ullage withthe one or more physical features identified in the adjusted model ofthe fuel tank.
 6. The method of claim 1, wherein generating the imagedata of the interior of the fuel tank comprises generating the imagedata using one or more image capturing devices located to generate theimage data of the interior of the fuel tank.
 7. The method of claim 6,wherein the one or more image capturing devices comprise a plurality ofimage capturing devices disposed at a plurality of locations to includea plurality of fields of view of the interior of the fuel tank.
 8. Adevice comprising: at least one processor; and computer-readable memoryencoded with instructions that, when executed by the at least oneprocessor, cause the device to: receive image data of an interior of afuel tank disposed within a wing of an aircraft; determine an amount ofwing bending of the wing of the aircraft based on the received imagedata of the interior of the fuel tank; produce a fuel measurement valuerepresenting an amount of fuel contained in the fuel tank based on theamount of wing bending of the wing of the aircraft; and output the fuelmeasurement value.
 9. The device of claim 8, wherein the received imagedata of the interior of the fuel tank disposed within the wing of theaircraft comprises active image data generated when the fuel tankcontains fuel; and wherein the computer-readable memory is furtherencoded with instructions that, when executed by the at least oneprocessor, cause the device to: receive reference image data of theinterior of the fuel tank; and determine the amount of wing bending ofthe wing of the aircraft by at least determining the amount of wingbending of the wing of the aircraft based on the active image data andthe reference image data.
 10. The device of claim 9, wherein thecomputer-readable memory is further encoded with instructions that, whenexecuted by the at least one processor, cause the device to determinethe amount of wing bending by at least causing the device to: determine,based on the active image data and the reference image data, adisplacement of one or more physical features of the interior of thefuel tank; and determine the amount of wing bending based on thedetermined displacement of the one or more physical features.
 11. Thedevice of claim 8, wherein the computer-readable memory is furtherencoded with instructions that, when executed by the at least oneprocessor, cause the device to produce the fuel measurement value by atleast causing the device to: adjust a model of a shape of the fuel tankbased on the determined amount of wing bending; and produce the fuelmeasurement value based on the adjusted model of the shape of the fueltank.
 12. The device of claim 11, wherein the computer-readable memoryis further encoded with instructions that, when executed by the at leastone processor, cause the device to produce the fuel measurement valuerepresenting the amount of fuel contained in the fuel tank based on theadjusted model of the shape of the fuel tank by at least causing thedevice to: identify, based on the generated image data, a location ofthe interior of the fuel tank corresponding to an interface of fuel andullage within the interior of the fuel tank; identify a location of anintersection of the interface of fuel and ullage with one or morephysical features identified in the adjusted model of the fuel tank; anddetermine a volume of fuel contained within the fuel tank based on theidentified location of the intersection of the interface of fuel andullage with the one or more physical features identified in the adjustedmodel of the fuel tank.
 13. The device of claim 8, wherein thecomputer-readable memory is further encoded with instructions that, whenexecuted by the at least one processor, cause the device to receive theimage data of the interior of the fuel tank by at least causing thedevice to receive the image data from one or more image capturingdevices located to generate the image data of the interior of the fueltank.
 14. A system comprising: one or more image capturing deviceslocated to generate image data of an interior of a fuel tank disposedwithin a wing of an aircraft; at least one processor; andcomputer-readable memory encoded with instructions that, when executedby the at least one processor, cause the system to: generate, using theone or more image capturing devices, the image data of the interior ofthe fuel tank disposed within the wing of the aircraft; determine andamount of wing bending of the wing of the aircraft based on thegenerated image data of the interior of the fuel tank; produce a fuelmeasurement value representing an amount of fuel contained in the fueltank based on the amount of wing bending of the wing of the aircraft;and output the fuel measurement value.
 15. The system of claim 14,wherein the generated image data of the interior of the fuel tankdisposed within the wing of the aircraft comprises active image datagenerated when the fuel tank contains fuel; and wherein thecomputer-readable memory is further encoded with instructions that, whenexecuted by the at least one processor, cause the system to: generate,using the one or more image capturing devices, reference image data ofthe interior of the fuel tank; and determine the amount of wing bendingof the wing of the aircraft by at least determining the amount of wingbending of the wing of the aircraft based on the active image data andthe reference image data.
 16. The system of claim 15, wherein thecomputer-readable memory is further encoded with instructions that, whenexecuted by the at least one processor, cause the system to determinethe amount of wing bending by at least causing the system to: determine,based on the active image data and the reference image data, adisplacement of one or more physical features of the interior of thefuel tank; and determine the amount of wing bending based on thedetermined displacement of the one or more physical features.
 17. Thesystem of claim 14, wherein the computer-readable memory is furtherencoded with instructions that, when executed by the at least oneprocessor, cause the system to produce the fuel measurement value by atleast causing the system to: adjust a model of a shape of the fuel tankbased on the determined amount of wing bending; and produce the fuelmeasurement value representing the amount of fuel contained in the fueltank based on the adjusted model of the shape of the fuel tank.
 18. Thesystem of claim 17, wherein the computer-readable memory is furtherencoded with instructions that, when executed by the at least oneprocessor, cause the system to produce the fuel measurement valuerepresenting the amount of fuel contained in the fuel tank based on theadjusted model of the shape of the fuel tank by at least causing thesystem to: identify, based on the generated image data, a location ofthe interior of the fuel tank corresponding to an interface of fuel andullage within the interior of the fuel tank; identify a location of anintersection of the interface of fuel and ullage with one or morephysical features identified in the adjusted model of the fuel tank; anddetermine a volume of fuel contained within the fuel tank based on theidentified location of the intersection of the interface of fuel andullage with the one or more physical features identified in the adjustedmodel of the fuel tank.
 19. The system of claim 14, wherein the one ormore image capturing devices comprise a plurality of image capturingdevices disposed at a plurality of locations to include a plurality offields of view of the interior of the fuel tank.
 20. The system of claim19, wherein an aggregate of the plurality of fields of view of theinterior of the fuel tank comprise an entirety of the interior of thefuel tank.